This invention relates to rotary worktables and indexing assemblies for use with machine tools.
Rotary worktables are well known in the prior art and have been employed in many systems for securing a particular workpiece for machining operations thereon. In order to position the particular workpiece so that the various machining operations can be performed at the precise location within the tolerances established, the rotary worktable is generally rotationally moved into various specific positions in order to provide the desired orientation for the workpiece. Typically, the rotary worktables are driven by worm gear drives which rotate the rotary worktable to the desired angular position. Unfortunately, the worm drives eventually develop inaccuracies in their tolerances due to wear on the drive teeth. As a result, the precision of these rotary tables deteriorates and their efficacy is progressively reduced.
Various rotary table indexing systems are typified by the following U.S. Pat. Nos.:
Price, 3,795,155; PA1 Frank et al, 3,889,555; PA1 Lahm, 3,717,912; PA1 Johnson, 2,989,874; PA1 Goebel, 3,724,291; PA1 Mazue, 3,824,877; PA1 Siebert, 3,772,961; PA1 Wahlstrom, 2,771,169.
Many of these patents have the common deficiency of having the indexing system incorporated and formed as part of the rotary drive system. Because of the wear placed upon these rotary drive teeth in moving the rotary worktables into the desired position, the teeth become worn and the precision of indexing becomes lost.
The Price, Lahm and Goebel patents all show disengageable detents or radial "curvic coupling" teeth employed to determine the successive angular positions of rotary index tables, but they all employ complex and expensive disengaging mechanisms.
Consequently, it is a principal object of the present invention to provide an economical rotary worktable which incorporates a precision indexing control system which is separate from the drive mechanism for the rotary table.
Another object of the present invention is to provide a rotary worktable incorporating the characteristic features described above in which the indexing control system can be automatically activated and automatically controlled to move the workpiece into a desired position.
Another object of the present invention is to provide a rotary worktable having the characteristic features described above which is capable of functioning for long periods of time without any loss of precision due to wear.
A further object of the present invention is to provide a rotary worktable having the characteristic features described above in which the indexing system can maintain angular precision within two minutes of arc.
Still another object of the invention is to provide rotary worktables of this character incorporating a ring-shaped pneumatic chamber, axially expansible and contractible, to transfer the worktable between an angular indexing rotatable mode and a locked machining mode, while the rotatable worktable face is not shifted, but is retained axially unmoved.
Other more specific objects will in part be obvious and will in part appear hereinafter.